Time Domian Electron Paramagnetic Resonance Imaging

项目一：时域电子顺磁共振成像：仪器：可编程定时单元：EPR成像中所需的射频脉冲在任何给定频率下的时间分辨率要求在纳秒范围内的时间分辨率，这与相同频率下的MRI实验不同。这是因为与核自旋动力学相比，顺磁自旋系统的自旋动力学更快。用于管理RF电路的定时单元在市场上不可用。我们已经设计，测试，并集成了一种新型的可编程定时单元与纳秒时间分辨率，控制所有的RF模块在光谱仪中使用一种新的方法，在RF电子利用LabView技术。集成该单元显著简化了光谱仪操作，因此通用用户无需RF工程专业知识即可使用扫描仪。此外，光谱仪的这种增加使该装置体积更小，并降低了为新购买的开放式磁体系统建造的第二个光谱仪的成本。开放式磁体系统：目前用于所有研究的磁体是1994年购买的，性能可靠。然而，小的孔尺寸和设计使得体内实验在容纳动物和具有麻醉、静脉注射管线等以及孔中的空气处理以将核心体温保持在37 ℃方面困难。为了克服这些困难，我们已经采购并安装了一个开放式磁体系统，该系统在水平面的两个方向（X和Y方向）上都可以进入，从而可以轻松地进行体内实验。磁体和梯度线圈已使用相应的放大器进行校准，控制软件已完成。RF链已集成，系统已准备就绪。EPRI-MRI联合成像的机架：由于基于EPR的pO 2图像缺乏解剖信息，因此解释氧图通常是不明确的。为了克服这一局限性，我们已经开发出的合作登记的EPR图像与MRI解剖图像的策略。EPRI中300 MHz的工作频率与在7 T下工作的MRI扫描仪的工作频率相似。因此，共同的共振器和机架的设计，测试，优化操作在两种模式，并用于顺序成像的对象与EPRI和RI没有移动的对象。这使得利用解剖学指导更可靠地解释氧图成为可能。体内EPRI和MRI联合成像：EPR成像可以显示肿瘤内氧浓度的分布，但不能提供解剖信息。EPRI/MRI组合系统可以了解肿瘤解剖结构中乏氧核心的确切位置，并且可以通过MRI结合氧状态和其他功能（包括血容量、血流量、水扩散等）对肿瘤生理进行多功能分析。构建了300 MHz脉冲EPR/氧成像系统，其中RF线圈和机架也被设计用于MRI。待测量的小鼠在EPR和MRI磁体之间转移，而无需将小鼠从线圈中取出，从而使EPRI的氧图和MRI的解剖结构的可靠且简单的共配准成为可能。使用该EPR/MRI共配准系统，正在进行肿瘤氧状态、其他参数（包括血液灌注、与肿瘤细胞性呈负相关的水扩散、MR光谱和放射治疗的结果输出）之间的关系。图像重建：目前使用的EPRI图像重建算法适用于Pentium PC。目前的情况是，数据集用于计算具有所需空间和生理分辨率的pO 2图像。需要2小时的计算时间来重新组织采集的数据，并额外花费30分钟来计算每个体素中的pO 2值。这给处理从体内实验中常规收集的图像数据带来了巨大的负担。为了减少图像重建时间，我们已经获得了一个基于Linux的四个双核集群CPU与2 TB的内存。目前，每当完成体模/动物体内血氧测定实验时，在采集机中采集的3-D血氧测定数据集通过网络I/O传输到并行服务器。在每次实验过程中创建一个唯一的索引文件，并由服务器用于构建PBS（并行批处理服务器）作业。通过机器的四个双核处理器自动运行多线程C程序来减少FID。使用自定义并行Matlab开发的图形用户界面（GUI）使用简化的数据集查看网格图，并根据用户提供的输入参数重建浓度图像和氧气图像。时间复杂度现在已经大大降低到几分钟的量级。Windows PC客户端通过桑巴舞（会话消息块）连接和SSH（安全外壳）连接到Linux服务器，使任何授权用户都可以运行GUI

Project 1: Time Domian Electron Paramagnetic Resonance Imaging: Instrumentation: Programmable Timing Unit: The time resolution of the radiofrequency pulses needed in EPR Imaging at any given frequency requires time resolution in nanosecond range unlike MRI experiments at the same frequency. This is because of the faster spin dynamics of paramagnetic spin systems compared to nuclear spin dynamics. The timing unit to manage the RF circuitry is not available commercially. We have designed, tested, and integrated a novel programmable timing unit with nanosecond time resolution which controls all the RF modules in the spectrometer using a new approach in RF electronics utilizing LabView technology. Integrating this unit resulted in simplifying the spectrometer operation significantly so that general purpose users can use the scanner without RF engineering expertise. In addition, this addition to the spectrometer made the unit less bulky and decreased the cost of the second spectrometer being built for the newly purchased open magnet system. Open Magnet System: The currently used magnet for all the studies was purchased in 1994 and has provided reliable performance. However, the small bore size and design makes in vivo experiments difficult in terms of housing the animal and have the anesthesia, iv lines etc and the air handling in the bore to maintain the core body temperature at 37 C. To overcome these difficulties, we have procured and installed an open magnet system with access in both directions in the horizontal plane (X- and Y-directions) so that in vivo experiments can be performed with ease. The magnet and gradient coils have been calibrated with the corresponding amplifiers and the control software completed. The RF chain is integrated and the system is ready for operation. Gantry for EPRI-MRI combined imaging: Since EPR based pO2 images lack anatomic information, interpreting the oxygen maps is often equivocal. To overcome this limitation, we have developed strategies for co-registering the EPR Images with anatomic images from MRI. The frequency of operation in EPRI of 300 MHz is similar to that of an MRI scanner operating at 7 T. Therefore a common resonator and gantry were designed, tested, optimized for operation in both modalities and used for sequential imaging of the object with EPRI and RI without moving the object. This made it possible to interpret the oxygen maps more reliable utilizing the anatomic guidance. In Vivo EPRI and MRI Co-Imaging: EPR imaging can visualize the distribution of oxygen concentration in tumor, though it doesnt provide anatomical information. The combined system of EPRI/MRI makes it possible to know the exact location of hypoxic core in the tumor anatomy, and also multi-functional analysis of tumor physiology combining the oxygen status and other functions by MRI including blood volume, blood flow, water diffusion etc. 300 MHz pulsed EPR/oxygen imaging system was constructed in which the RF coil and gantry were designed to also be used for MRI. The mouse to be measured is transferred between EPR and MRI magnets without removing the mouse from the coil, making reliable and simple co-registration of oxygen map by EPRI and anatomy by MRI possible. Using this EPR/MRI co-registration system, the relationship among tumor oxygen status, other parameters including blood perfusion, water diffusion which inversely related with tumor cellularity, MR spectroscopy, and resulting output of radiation therapy is underway. Image Reconstruction: The currently used EPRI image reconstruction algorithms are adapted on a Pentium PC. The current situation is that the data sets are to calculate the pO2 images with the required spatial and physiological resolutions. It takes 2 hours computational time to reorganize the acquired data and an additional 30 minutes to calculate the pO2 values in each voxel. This imposes enormous burden to process routinely collected image data from in vivo experiments. To reduce the image reconstruction time, we have acquired a Linux-based four dual-core cluster CPU with a 2 TB memory. Currently, whenever the phantom/animal in-vivo oximetry experiment is completed, the 3-D oximetry data sets that are collected in the collection machine are transferred to the Parallel Server via network I/O. A unique index file is created during every experiment and used by the server to construct PBS (Parallel Batch Server) job. The FIDs are reduced by automatically running a multi-threaded C program by the four dual-core processors of the machine. A graphical user interface (GUI) developed using custom parallel Matlab, uses the reduced data sets to view the mesh plots and to reconstruct the concentration images and oxygen images depending upon the input parameters provided by the user. The time complexity has now drastically reduced in the order of few minutes. A Windows PC client to Linux server connection via Samba (Session Message Block) connectivity and SSH (Secure Shell) enables any authorized users to run the GUI